Melting glaciers redistribute Asia's water

"The glacier at Karo-la pass covered the whole rock face when our Tibetan guide began leading tours in 1996."

I spent the October holiday in China traveling across the Tibetan plateau to Qomolangma (Mount Everest) base camp. One striking impression was how much water there is there. Most of the great rivers of Asia originate on the Qinghai-Tibet plateau: Ganges, Indus, Yangtze, Yellow, Mekong, Salween, Irrawady, and Yarhung Tsangpo (which becomes the Brahmaputra in India and Bangladesh). Half the world’s population gets its water from these rivers running off the plateau. The rivers are fed by the gradual melting of the huge glaciers that cover the Himalayan peaks, as well as the melting of the annual snowpack and seasonal rain. (The name of the Himalayan peak, Annapurna, in Nepal means “full of food,” reflecting the fact that the gradual melting of snowpack and glaciers each spring and summer waters the rice crop.)

The melting of the glaciers has accelerated dramatically in recent years. This is one of the most profound effects of global warming. The glaciers have shrunk 20% over the past 50 years, with much of that in the past decade. Our Tibetan guide took us to a number of different glaciers and showed us how they had receded since he starting taking tours around in 1996. At Karo-la pass we stood on hard, dry ground that had been covered by the glacier just 12 years ago. Climate scientists project that the glaciers will be 80% gone by 2035.

The implication of the accelerated melting is already being felt around Asia. In the short run the faster melting leads to greater summertime flow in the rivers coming off the plateau, exacerbating the seasonal flooding that has always plagued the region. In recent years there have been some unusually severe floods in South China, India, and elsewhere in Asia. In the long run the disappearance of the glaciers will lead to persistent droughts in various locations around Asia. Global climate change does not seem to be changing the total amount of water available in Asia, but it is redistributing it both across time and across space.

Glaciers on Qomolangma (Mt. Everest) and other peaks on the Tibetan plateau are shrinking rapidly.

North China is one of the areas likely to be hit with increasing water scarcity. China overall is not a water rich country per capita. Furthermore, most of the water is now in the South, whereas 42% of the population lives in the North. As a result, North China has only one-ninth the world average availability of water. Agriculture throughout the North faces the challenge of diminished river flow and falling water tables. Most Northern cities have persistent water shortages.

Adjusting to the drier environment in North China is a big challenge. One option, long in the planning, is to divert water from Southern rivers to Northern ones. This option is expensive, energy-intensive, and environmentally risky. Other options are: (1) to use the existing water more productively; and/or (2) to facilitate migration from the North to the South. The current use of water is quite inefficient in the sense that the GDP generated by one cubic meter of water is much higher in some activities than in others. Creating water markets and pricing water economically would encourage it to be allocated to its most productive use. In practice this would shift Northern agriculture away from water-intensive crops such as grain toward higher value-added products including certain vegetables, tree crops, and flowers. It would also make urbanization proceed more smoothly because cities would be able to get the water they need as long as they priced it appropriately for their households and firms.

Migration from North to South is something of a controversial idea. It will tend to happen naturally in the absence of restrictions on mobility. There is a long-run tendency for the population to shift from rural/agricultural activities to urban ones, because productivity in China is much higher in cities than in the countryside. As this process occurs, it is easier for Southern cities to expand than Northern ones, because of the availability of water.

China is fortunate to be a large country, which has several implications for this issue. First, China’s own activities will have a significant effect on climate change. If the country meets its ambitious targets for increasing energy efficiency, that will limit the rise in temperatures, especially if it’s part of a global effort to reduce greenhouse gas emissions. Second, the spatial redistribution of water from North to South can be partly addressed through migration, since it is all within one country. Elsewhere in Asia there may be redistribution of water among countries as a result of climate change, which would lead to tensions and in the worst case, conflict.

Seeing the big rivers and glaciers in Tibet, it is hard to imagine a water-scarce world. But then these rivers quench the thirst of more than 3 billion people. Hence any significant change in their basic flow patterns as a result of climate change will force large adjustments. Hearing from local people about how the glaciers have receded in recent years left me really worried.